The Lithospheric Conductivity Structure Across The Yadong-Gulu Rift On Tibetan Plateau

In southern Tibetan plateau,a series of north � south trending grabens and rifts are distributed from west to east,which are closely related to the extension of upper crust,the characteristics of the underthrusting Indian lithospheric slab and the ore deposites distribution of Gangdese metallogenic belt.Located in the eastern side of the plateau,Yadong-Gulu rift(YGR)is the longest one and the lithospheric conductivity structure across it may provide significant information about the extension of upper crust,the charactersistics of the underthrusting Indian lithospheric slab and the ore deposites distribution.The magnetotelluric(MT)method,using the natural electromagnetic field as source,can provide the interior conductivity structure of the whole lithosphere effectively.After standard data processig,dimensionality analysis and regional strike analysis,both 2D and 3D inversion of the magnetotelluric data across the northern segment of the YGR in Lasha terrane were conducted to derive the reliable conductivity model.The result reveals that the upper crust to the east of YGR is significantly intruded by the underlying conductors;the conductors in the middle crust are not continuous in the east-west direction;there is a deep conductor underneath the YGR.Based on the features of the conductivity model from this study and other geophysical observations,the formation of the YGR is most likely caused by the tearing of the oblique underthrusting Indian lithospheric slab through the pull of mid-lower crustal conductors that have locally weak strength beneath the YGR.Since the larger underthrusting angle or local delamination of the Indian lithospheric slab to the east of YGR,the hot asthenospheric material in the mantle wedge may provide more heat and metals for the crust.The result also shows that the ore deposits in Gangdese metallogenic belt are not only related to the electrical interfaces in the shalow crust,but also closely linked to the conductors in the middle crust through the buried north�south-direction faults in the upper crust.The intersections of the extensional structures in north-south direction and the thrust in east-west direction are probably the important metallogenic zones.